Variable air filter assemblies

ABSTRACT

An air filter assembly includes a filter element having at least one variable dimension, and a frame for engaging and supporting the filter element. The frame may include a plurality of linear segments forming a rectangular configuration, and a plurality of clips for connecting the linear segments together at corners thereof. The linear segments may be L-channel segments, C-channel segments, or may be of other form. Clips may be used for connecting the linear segments together at the corners. The filter element may have a pattern of creases or fold lines to facilitate folding thereof from an expanded configuration to a reduced configuration. A grate may be included for spanning an area bounded by the frame to support the filter element. The grate may have multiple arms and a central hub. An edge treatment may form a seal between the filter element and the frame.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 16/288,304 filed on Feb. 28, 2019, which claims thebenefit of priority of: U.S. provisional patent application No.62/636,581, titled “Systems, Components, Devices, and Methods forFoldable and Expandable Air Filters” filed on Feb. 28, 2018; and U.S.provisional patent application No. 62/694,091, titled “Variable AirFilter Assemblies,” filed on Jul. 5, 2018, each of which is incorporatedherein in its entirety by this reference.

TECHNICAL FIELD

The present disclosure relates to devices for air filtration. Moreparticularly, the present disclosure relates to variably sized airfilter assemblies.

BACKGROUND

Air filters for capturing dust, particulate matter, and other airbornematerials such as animal hair and dander are available in varieties ofprescribed rectangular sizes that are typically incremented by inchesalong each of two sides. Each typical home or business HVAC air-handlingsystem requires periodic or occasional replacement of a particularlydimensioned filter, and consumers are thus burdened with finding anappropriately sized replacement. In reality, the receptacle structuresof the air-handling systems are ultimately not precisely dimensionedaccording to even their nominal dimensions, and so even when anappropriately labeled filter is found, a perfect fit, with well-sealededges, without any deformation of the replacement filter is ultimatelynot assured.

Compromises are thus made, including for example the use of filters thatare bit small or large in one or both rectangular dimensions, andfrustrated consumers even delay or neglect suggested periodic filterreplacement. When air driven through an air-handling system bypasses animproperly fitted filter, airborne matter is not optimally trapped atthe filter, which can permit the accumulation of matter on HVAC systemcomponents and cause or aggravate respiratory problems. When filterreplacement schedules are missed, filter blockage by matter accumulatedin an old filter can increase system power consumption and wear, and canharbor microbial growth, which also can also adversely affectrespiratory health.

SUMMARY

This summary is provided to briefly introduce concepts that are furtherdescribed in the following detailed descriptions. This summary is notintended to identify key features or essential features of the claimedsubject matter, nor is it to be construed as limiting the scope of theclaimed subject matter.

An air filter assembly according to at least one embodiment includes afilter element having at least one variable dimension, and a frame forengaging and supporting the filter element.

The frame may include a plurality of linear segments forming arectangular configuration.

The linear segments may include at least one L-channel segment.

The linear segments may include at least one C-channel segment.

The air filter assembly may further include a plurality of clips forconnecting the linear segments together at corners of the rectangularconfiguration.

The air filter assembly may further include at least one elasticizedcord joining the linear segments.

The elasticized cord may have two terminal ends engaged together by atleast one connector.

The elasticized cord may include a first end having a first connector;and a second end comprising a second connector.

The first connector may include a first magnet, and wherein the secondconnector may include a second magnet.

The linear segments form a rectangular configuration of variabledimensions.

The linear segments may be formed by bending or segmenting a primarystrip into four segments.

Each of the linear segments may include a slotted edge, and two of thelinear segments may engage when a slot of the slotted edge of one linearsegment aligns with a slot of the slotted edge of another linearsegment.

The frame may include a flexible arm biased toward a linear state.

The flexible arm may include a spring steel element having acylindrically concave side and an opposing cylindrically convex side.

The profiled spring steel element may be self-biased toward a linearstate, in which it extends along a longitudinal channel axis definedalong the cylindrically concave side.

The air filter assembly may further include at least one grate elementspanning an area defined by the frame for supporting the filter element.

The at least one grate element may include an elasticized cord passedthrough holes defined in the frame.

The frame may include frame elements having portions that areoverlapped, and wherein the elasticized cord is passed through alignedholes in the overlapping portions thereby maintaining engagement of theframe elements.

The frame elements may include linear segments and corner pieces havingoverlapping portions maintained in engagement by the elasticized cord.

The grate element may include multiple parallel arms.

Each arm may include, at each of two ends thereof, a respective toothfor engaging the frame.

The arms may be interconnected by and regularly spaced along a cord.

The arms and cord may be rollable into a bundle.

The frame may include a first frame section having first teeth, and asecond frame section having second teeth. The two frame sections may beconfigured to capture at least a portion of the filter element betweenthe first teeth and second teeth when interlocked.

The at least one edge portion filter element may extend outward from theframe and captured portion of the filter element to define a gasket.

The air filter assembly may include a grate assembly having posts foraligning with and engaging notches defined by the frame.

The notches may each be wedge shaped, having an open mouth and narrowingtoward a hole for receiving and retaining a post of the grate assembly.

The frame may include a frame segment having at least a first slot forretaining an edge of the filter element.

The air filter assembly may further include a screen, and the framesegment may have a second slot for retaining an edge of the screen.

The filter element may include a filter medium and an edge cuff mountedon an edge of the filter medium, and the edge cuff may be configured tobe removably captured in the first slot.

The frame may include a folding hub and arms connected to the foldinghub.

The arms may be connected to the filter element.

The folding hub may have a folded configuration and an expandedconfiguration.

The air filter assembly may further include an edge treatment forforming a peripheral seal.

The filter element may have a pattern of creases or fold lines tofacilitate folding thereof from an expanded configuration to a reducedconfiguration.

The filter element may include a filter media element for filtering airpassed therethrough, the filter media element may have at least oneperipheral edge, and an edge treatment for attachment to the peripheraledge of the filter media element.

The edge treatment may include a deformable gasket, flange, or layer forforming a seal at the peripheral edge of the filter media element.

The edge treatment may form a seal between the filter media element andthe frame.

The filter element may be twice foldable from an expanded rectangularconfiguration to a reduced configuration for shipping or storage.

The filter element may have a preformed fold pattern that facilitatesreduction in two-dimensions.

BRIEF DESCRIPTION OF THE DRAWINGS

The previous summary and the following detailed descriptions are to beread in view of the drawings, which illustrate particular exemplaryembodiments and features as briefly described below. The summary anddetailed descriptions, however, are not limited to only thoseembodiments and features explicitly illustrated.

FIG. 1A shows a variable filter assembly according to at least oneembodiment.

FIG. 1B shows a frame of the variable filter assembly of FIG. 1B aslinear segments of a C-channel strip, according to at least oneembodiment.

FIG. 1C shows terminal ends of the folded strip of FIG. 1B joined.

FIG. 1D shows holes formed in the strip joining and mutually engagingthe terminal ends of FIG. 1C, according to at least one embodiment.

FIG. 1E shows edges of a filter media element wrapped partially aroundrespective frame segments according to at least one embodiment.

FIG. 1F shows the wrapped edges of the filter media element of FIGS. 1Aand 1E secured by spike bars according to at least one embodiment.

FIG. 2A shows a variable filter assembly according to at least oneembodiment.

FIG. 2B shows a single elasticized cord grate layer, according to atleast one embodiment.

FIG. 2C shows a double elasticized cord grate layer according to atleast one embodiment.

FIG. 2D shows pole segments of the frame of the filter assembly of FIG.2A, according to at least one embodiment.

FIG. 2E the pole segments of FIG. 2D arranged in a rectangular form,according to at least one embodiment.

FIG. 2F shows a grate hook placed along a pole segment, according to atleast one embodiment.

FIG. 2G is cross section of a pole segment and grate hook according toat least one embodiment.

FIG. 3A shows a variable filter assembly according to at least oneembodiment.

FIG. 3B shows a frame of the filter assembly of FIG. 3A, includingcrossed linear frame segments according to at least one embodiment.

FIG. 3C shows the crossed frame segments engaged at their intersectionaccording to at least one embodiment.

FIG. 4A is a variable frame assembly according to at least oneembodiment.

FIG. 4B shows a bend area of an L-channel of the frame of the assemblyof FIG. 4A, according to at least one embodiment.

FIG. 4C shows a linear strip from which the frame is formed, accordingto at least one embodiment.

FIG. 4D shows a corner junction of the frame, according to at least oneembodiment.

FIG. 4E shows a corner junction of FIG. 4D secured by a clip, accordingto at least one embodiment.

FIG. 5A shows a modular frame assembly, according to at least oneembodiment.

FIG. 5B shows an L-channel segments of the frame assembly of FIG. 5A,according to at least one embodiment.

FIG. 5C shows a corner junction of two segments with a corner clip,according to at least one embodiment.

FIG. 5D shows an L-channel segment of the frame as notched, according toat least one embodiment.

FIG. 5E shows an L-channel segment of the frame as stamped, according toat least one embodiment.

FIG. 6A shows a frame in an expanded state, according to at least oneembodiment.

FIG. 6B shows the frame of FIG. 6A in a first reduced state and with agrate assembly, according to at least one embodiment.

FIG. 6C shows the frame of FIG. 6A in a second reduced state.

FIG. 7A shows a frame in an expanded state, according to at least oneembodiment.

FIG. 7B shows the frame of FIG. 7A in a first reduced state and with agrate assembly, according to at least one embodiment.

FIG. 7C shows the frame of FIG. 7A in a second reduced state.

FIG. 8A shows a frame and a grate assembly according to at least oneembodiment.

FIG. 8B shows the grate assembly of FIG. 8A in a planar state.

FIG. 8C shows a portion of the grate assembly of FIG. 8A in a closerview.

FIG. 8D shows the grate assembly of FIG. 8A in a partially rolled state.

FIG. 9A shows a frame and a grate assembly according to at least oneembodiment.

FIG. 9B shows an arm of the grate assembly of FIG. 9A.

FIG. 10A shows a variable filter assembly according to at least oneembodiment.

FIG. 10B shows the filter media element of FIG. 10A.

FIG. 10C shows the filter media element of FIG. 10A collapsed andbended.

FIG. 10D shows the filter media element of FIG. 10B further reduced to ashipping size.

FIG. 10E shows a close view of the corner portion of the filter assemblyof FIG. 10A.

FIG. 11A is a filter media element in a sized minimized state, accordingto at least one embodiment.

FIG. 11B is the filter media element in a state reached by onceunfolding from the state of FIG. 11A.

FIG. 11C is the filter media element in a state reached by twiceunfolding from the state of FIG. 11A

FIG. 11D is a frame according to at least one embodiment.

FIG. 11E is a filter assembly in which the filter media element in thestate of FIG. 11C is engaged with the frame of FIG. 11D, according to atleast one embodiment.

FIG. 12A is an exploded perspective view of a filter assembly accordingto at least one embodiment.

FIG. 12B shows interlocking teeth frame sections along an edge portionof the filter assembly of FIG. 12A.

FIG. 12C is an enlarged perspective view of a corner portion of thefilter assembly of FIG. 12A.

FIG. 13A shows a variable frame according to at least one embodiment.

FIG. 13B shows a portion of a linear segment of the frame of FIG. 13A,according to at least one embodiment.

FIG. 13C shows a corner portion of a mesh/grid, according to at leastone embodiment.

FIG. 13D shows a variable frame and grate assembly according to at leastone embodiment.

FIG. 13E shows a corner portion of the variable frame and grate assemblyof FIG. 13D.

FIG. 14 shows a cover for a filter assembly, according to at least oneembodiment.

FIG. 15A shows an expandable filter media element, according to at leastone embodiment, in a first configuration.

FIG. 15B shows the expandable filter media element of FIG. 15A in asecond configuration.

FIG. 15C shows the expandable filter media element of FIG. 15A in athird configuration.

FIG. 16A shows components an unassembled frame assembly, according to atleast one embodiment.

FIG. 16B shows the components of FIG. 16a positioned for assembly.

FIG. 17 shows a filter assembly according to at least one embodiment.

FIG. 18A shows a frame with cross arms according to at least oneembodiment.

FIG. 18B shows a filter media element according to at least oneembodiment.

FIG. 18C shows a filter assembly including the frame of FIG. 18A andfilter media element of FIG. 18B, according to at least one embodiment.

FIG. 19 shows a filter assembly, according to at least one embodiment,in an expanded rectangular configuration.

FIG. 20A shows the filter assembly of FIG. 19, in a once-foldedconfiguration.

FIG. 20B shows the filter assembly of FIG. 19, in a twice-foldedconfiguration.

FIG. 20C shows the filter assembly of FIG. 20B, in a package forshipping or storage.

FIG. 21A shows a foldable filter media element, according to at leastone embodiment.

FIG. 21B shows the filter media element of FIG. 21A in transition to afolded reduced state.

FIG. 21C shows the filter media element of FIG. 21A in a folded reducedstate.

FIG. 22A is a shipping or storage package for use with a filter mediaelement, according to at least one embodiment.

FIG. 22B is the package of FIG. 22B with a filter media element placedinside, according to at least one embodiment.

FIG. 23 is a side view of an edge portion of a filter assembly accordingto at least one embodiment.

FIG. 24 is a side view of an edge portion of a filter assembly accordingto at least one embodiment.

FIG. 25 is a side view of an edge portion of a filter assembly accordingto at least one embodiment.

FIG. 26 is a side view of an edge portion of a filter assembly accordingto at least one embodiment.

FIG. 27 is a side view of an edge portion of a filter assembly accordingto at least one embodiment.

FIG. 28 is a side view of an edge portion of a filter assembly accordingto at least one embodiment.

FIG. 29A shows a filter assembly, according to at least one embodiment.

FIG. 29B shows the frame of the filter assembly of FIG. 29A.

FIG. 30A shows a filter assembly, according to at least one embodiment,having a frame and a filter element in place for use.

FIG. 30B shows the filter assembly of FIG. 30A, with the filter elementraised.

FIG. 31A shows a filter assembly, according to at least one embodiment,having a frame and a filter element in place for use.

FIG. 31B shows the filter assembly of FIG. 31A, with the filter elementraised.

FIG. 32A shows a filter assembly, according to at least one embodiment,having a support insert in place.

FIG. 32B shows the filter assembly of FIG. 32A, having the supportinsert raised.

FIG. 33A shows a filter assembly, according to at least one embodiment,having a filter media element and a support insert.

FIG. 33B shows the filter media element of FIG. 33A.

FIG. 33C shows the support insert of FIG. 33A in a collapsed state.

FIG. 34A shows a filter assembly, according to at least one embodiment,having a filter media element and a support insert.

FIG. 34B shows the support insert of FIG. 34A in a disassembled state.

FIG. 34C shows the filter media element of FIG. 34A.

FIG. 35A shows a filter element in a package, according to at least oneembodiment.

FIG. 35B shows the filter element of FIG. 35A at least partiallyexpanded.

FIG. 35C shows a corner portion of the filter element of FIG. 35Apositioned to engage a frame.

FIG. 36A shows a frame and grate for a filter assembly according to atleast one embodiment.

FIG. 36B shows the frame and grate of FIG. 36A, with the framedisassembled.

FIG. 36C shows multiple alternative grid patterns, according to variousembodiments.

FIG. 37A is a view of an edge portion of a filter assembly, according toat least one embodiment.

FIG. 37B is a perspective view of a peripheral frame segment and mountedbezel clip of FIG. 37A, according to at least one embodiment.

FIG. 37C is a view of the frame segment of FIG. 37A.

FIG. 37D is a view of the bezel clip of FIG. 37A.

FIG. 38A shows a portion of a filter media element, according to atleast one embodiment.

FIG. 38B is a filter assembly, according to at least one embodiment, inwhich the filter media element of FIG. 38A is used.

FIG. 38C is another view of the filter assembly of FIG. 38B.

FIG. 39A shows a filter assembly according to at least one embodiment.

FIG. 39B shows a folding bracket hub, according to at least oneembodiment, of the filter assembly of FIG. 39A in a folded state.

FIG. 39C shows the folding bracket hub of the filter assembly of FIG.39A in ninety degree or half-opened state.

FIG. 39D is a perspective view of the folding bracket hub of the filterassembly of FIG. 39A in fully unfolded or opened state.

FIG. 39E shows the filter assembly of FIG. 39A in a folded state.

FIG. 40A shows a filter assembly, according to at least one embodiment,in an expanded planar state.

FIG. 40B shows the filter assembly of FIG. 40B, in a partially foldedstate.

FIG. 40C shows the filter assembly of FIG. 40B, in a further foldedstate.

FIG. 41A shows two separated components of the folding bracket hub ofFIG. 39B, according to at least one embodiment.

FIG. 41B is a plan view of the folding bracket hub in the state of FIG.39D, according to at least one embodiment.

FIG. 41C is an elevation view of the folding bracket hub in the state ofFIG. 39D, according to at least one embodiment.

FIG. 42 shows a variety of arms for use with the folding bracket hub ofFIG. 39B, according to various embodiments.

FIG. 43A is a perspective view of an edge treatment for a filter mediaelement, according to at least one embodiment.

FIG. 43B is another perspective view of the edge treatment of FIG. 43A.

FIG. 44 shows an expandable filter media element having an advantageousfold pattern according to at least one embodiment.

FIG. 45A shows an expandable filter media element having an advantageousfold pattern according to at least one embodiment.

FIG. 45B is shows a filter assembly in an expanded state, according toat least one embodiment.

FIG. 46A shows a filter assembly including a filter media element havinganother advantageous fold pattern, according to at least one embodiment.

FIG. 46B shows a profiled spring steel element for use in arms thatreturn the filter media element of FIG. 46A to its illustrated planarstate once released from packaging, according to at least oneembodiment.

FIG. 47A shows a first side of an expandable filter element, accordingto at least one embodiment, having a preferential fold pattern tofacilitate two-dimensional reduction.

FIG. 47B shows a pleated paper top layer of the filter element of FIG.47A, according to at least one embodiment.

FIG. 47C shows a foam substrate of the filter element of FIG. 47A,according to at least one embodiment.

FIG. 48A is another view of the expandable filter element of FIG. 47A,according to at least one embodiment.

FIG. 48B shows a foam element for use as a frame edge mounted on theexpandable filter element of FIG. 47A, according to at least oneembodiment.

FIG. 49 shows a filter having a creased filter media element with anadvantageous fold pattern to facilitate two-dimensional reduction,according to at least one embodiment.

FIG. 50 shows a filter assembly, according to at least one embodiment.

FIG. 51 shows a first side of the folding grate of FIG. 50, without afilter media element.

FIG. 52 shows a second side of the folding grate of FIG. 50.

FIG. 53 shows an expandable filter element, according to at least oneembodiment, in which a folding hub has an open central area.

FIG. 54 is an enlarged view of a central portion of the filter elementof FIG. 53.

FIG. 55 shows the folding hub of FIG. 53 without a filter media element.

DETAILED DESCRIPTIONS

These descriptions are present particular embodiments with sufficientdetails to provide an understanding of broader inventive subjectmatters. These descriptions expound upon and exemplify particularfeatures of those particular embodiments without limiting the inventivesubject matters to the explicitly described embodiments and features.Considerations in view of these descriptions will likely give rise toadditional and similar embodiments and features without departing fromthe scope of the inventive subject matters.

Any dimensions expressed or implied in the drawings and thesedescriptions are provided for exemplary purposes. Thus, not allembodiments within the scope of the drawings and these descriptions aremade according to such exemplary dimensions. The drawings are not madenecessarily to scale. Thus, not all embodiments within the scope of thedrawings and these descriptions are made according to the apparent scaleof the drawings with regard to relative dimensions in the drawings.However, for each drawing, at least one embodiment is made according tothe apparent relative scale of the drawing.

Unless described or implied as exclusive alternatives, featuresthroughout the drawings and descriptions should be taken as cumulative,such that features expressly associated with some particular embodimentscan be combined with other embodiments.

The drawings illustrate various embodiments of filter assemblies andtheir components including, for example, frames, filter elementssupported along their outer edges by frames, and grates that span theareas defined between frame elements to further support the filterelements. The filter elements include filter media elements forfiltering air passed therethrough. The filter media elements aregenerally porous and may be layered and may include woven and non-wovenmaterials such as fabrics, piles, felts, and foams. The media elementsmay include materials that are spun bonded or molded. The media elementsmay include materials having antimicrobial properties. Other filtermedia materials and properties are within the scope of thesedescriptions. In some cases, the filter elements include sub-frames andvarious particular layers and edge treatments.

Throughout, some degree of size variability of the frames, filterelements, and other components is enabled by the drawings anddescriptions. The descriptions describe features with reference to afilter plane, referring to a generally planar configuration or geometryof a filter assembly deployed and ready for use.

FIG. 1A shows a variable filter assembly according to at least oneembodiment having a frame termed herein as a “foldable simple frame.”The assembly includes an expandable filter media element 110 supportedby a peripheral frame 100 of linear segments arranged in a rectangularform in the filter plane. As shown in FIG. 1B, the linear segments 102are formed by folding a C-channel strip 104, which is foldable anywherealong its length, at spaced fold locations according the dimensionsdesired. The terminal ends of the folded strip are then cut to length,to remove any excess strip material, and joined as shown in FIG. 1C.Holes formed along the strip facilitate measuring and folding to formsegments, and facilitate joining the two end segments at their terminalends as shown in FIG. 1D. As shown in FIGS. 1E and 1F, edges of thefilter media element 110 can be wrapped partially around a respectiveperipheral frame segment 102 and secured thereto by a respective spikebar 106. Each spike bar 106 has spikes spaced equivalently as the holesin the C-channel strip 104 from which the linear frame segments 102 areformed.

FIG. 2A shows a variable filter assembly according to at least oneembodiment having a frame 200 termed herein as a “pole frame.” Theassembly includes an expandable filter media element 210 supported bythe peripheral frame 200, which has tubular pole segments 202 arrangedin a rectangular form in the filter plane. The pole segments are joinedby an internally captured shock cord 204 (FIG. 2D) having two opposingends terminating at respective connectors 206, which may be magnetic.The shock cord can be an elasticized cord, such as a bungee cord, havingelastic strands forming a core covered in a woven fibrous sheath, forexample made of polypropylene or other natural or synthetic fibers. Theframe is maintained in a rigid configuration by tension of the shockcord 204 when the pole segments are arranged in the rectangular form andthe two connectors at the ends of the shock cord are joined as shown inFIG. 2E. Secondary shock cord segments 222 stretched across thefiltration area of the expanded filter media element form an expandablegrate 220. Grate hooks 224 through which the secondary shock cordsegments are passed can slide along the pole segments as shown in FIG.2F to vary the grate pattern. Each grate hook 224, as shown in FIG. 2G,has a bolt movably captured within a pole segment, a shank extendingfrom the bolt through a longitudinal slit formed in the wall of the polesegment, and a loop or eye carried by the shank for engaging a shockcord segment.

FIG. 3A shows a variable filter assembly according to at least oneembodiment having a frame termed herein as a “box divider.” The assemblyincludes an expandable filter media element 310 supported by a segmentedframe 300 of linear frame segments 302 arranged as crossed in anhourglass form in the filter plane. The linear segments are formed byfolding and segmenting a notched strip 304 (FIG. 3B) having spacednotches 306 along a longitudinal edge. The frame segments mutuallyengage when the slotted edge of one segment is brought into engagementwith another where two notches align at the intersection of two framesegments as shown in FIG. 3C. The hourglass form is defined by twoparallel outer frame segments and two inner frame segments crossing andintersecting at the center of the frame as shown in FIG. 3B. The filtermedia element can be expanded onto the frame with marginal portions ofthe filter media element adhered to the outer frame segments. Onceassembled, the variable filter assembly has an overall outer rectangularform.

FIG. 4A shows a variable frame assembly 400 according to at least oneembodiment termed herein as a “foldable frame.” The assembly includesfour linear L-channel segments 402 defining an outer rectangular form ofvariable dimensions. The linear segments are formed by bending orsegmenting a primary strip 404 into four segments (FIG. 4C). The striphas a longitudinal crease or embossed line 408 that extends the lengthof the strip between its longitudinal edges to facilitate formation ofthe L-channel segments by 90 degree fold of each segment about thecrease or embossed line 408 (FIG. 4C). The four corner junctions (FIG.4D) of the segments are maintained by a corner clip 406 (FIG. 4E) ateach corner. The variable frame assembly is useful to support orstrengthen various filter assembly embodiments described herein.

FIG. 5A shows a frame assembly 500 according to at least one embodimenttermed herein as a “modular frame with corner clips.” The assemblyincludes four linear L-channel segments 502 (FIG. 5B) defining an outerrectangular form of variable dimensions in the filter plane. The linearsegments are formed by bending or segmenting a primary strip 504 (FIGS.5D-5E) into four segments. The strip 504 has a longitudinal crease orembossed line that extends the length of the strip between itslongitudinal edges to facilitate formation of the L-channel segments by90 degree fold of each segment at the crease or embossed line. The fourcorner junctions of the segments are maintained by a corner clip 506(FIG. 5C) at each corner. The variable frame assembly is useful tosupport or strengthen various filter assembly embodiments describedherein.

FIG. 6B shows a frame and grate assembly according to at least oneembodiment, having a frame termed herein as a “collapsible frame.” Theassembly includes a frame 600 (FIG. 6A) having four linear L-channelsegments 602, and four L-channel 90-degree bend corner pieces 606. Thelinear segments can variably overlap linear portions extending from thecorner pieces to define an outer rectangular form of variabledimensions. Preformed holes in the L-channel faces corresponding to thefilter plane are regularly spaced to as to align at incremental variabledimensions. A flexible tensile cord 620, such as a shock cord, is lacedthrough the holes forming a grate across the area within the frame inthe filter plane. The cord, passing through aligned respective holes ofoverlapping portions of the linear-segment and corner-piece frameelements, maintains engagement of the linear segments and corner piecesat desired dimensions of the frame. The frame 600 in FIG. 6B is reducedin a first direction relative to the expanded state of FIG. 6A. Theframe 600 in FIG. 6C is further reduced in a second directionperpendicular to the first direction.

FIG. 7 A shows a frame and grate assembly 700 according to at least oneembodiment, termed herein as a “collapsible frame+grid.” The assembly700 includes four corner area pieces 706 and multiple edge area pieces702 arranged according to desired outer rectangular dimensions. Each ofthe corner area pieces and edge area pieces has peripheral L-channelframe segments and additional frame arms extending therefrom in thefilter plane to together define a grate. Three configurations are shownby varying the overlapping arrangement of corner area and edge areapieces. In the largest of the configurations shown, a central gridsection 720 is installed in the filter plane between edge area pieces.The frame 700 in FIG. 7B is reduced in a first direction relative to theexpanded state of FIG. 7A. The frame 700 in FIG. 7C is further reducedin a second direction perpendicular to the first direction.

FIG. 8A shows a frame 400, for example as shown in FIG. 4A, and a grateassembly 820 according to at least one embodiment, termed herein as a“grid roll.” The grate assembly includes multiple parallel grate arms822 (FIG. 8C) each having, at each end thereof, a tooth 824 for piercingthe filter plane portions of the frame segments. The grate arms areinterconnected and regularly spaced along a cord 826, which may beinextensible or may be of variable length such as a shock cord. Thegrate arms can be conveniently rolled (FIG. 8D) into a bundle forshipping and storage. The grate assembly 820 (FIGS. 8A-8B) can also beused with frames (FIGS. 4A and 5A for example) where holes toaccommodate the teeth are to be formed by piercing frame segments, andused with frames (for example FIG. 6A) where holes are already formed inthe frame in the filter plane.

FIG. 9A shows a frame 400, for example as shown in FIG. 4A, and a grateassembly 920 according to at least one embodiment, termed herein as a“fold & snap grate.” The grate assembly 920 includes multiple grate arms922 each having, at each end thereof, a tooth 908 for piercing orengaging the filter plane portions of the frame segments. As shown inFIG. 9B, each grate arm is formed from a strip 904 have regularly spacednotches 906 where the strip can be terminated or folded. The teethextending from the grate arm are the two inter-notch sections of thestrip at its ends folded to 90 degrees. Each tooth can be passed throughthe frame segment and folded flat to secure the ends of each grate arm.The grate assembly 920 can also be used with frames (FIGS. 4A and 5A forexample) where holes to accommodate the teeth are to be formed bypiercing frame segments and used with frames (for example FIG. 6A whereholes are already formed in the frame in the filter plane.

FIG. 10A shows a variable filter assembly according to at least oneembodiment having a filter media element 1010 termed herein as a“magnetic fold up filter.” The expandable filter media element issupported by a peripheral frame 1000 of linear segments arranged in arectangular form in the filter plane. The frame segments and filtermedia element are engaged by magnetic attraction (FIG. 10E), in at leastone embodiment. The filter media element 1010 can be collapsed alongparallel accordion fold lines 1012 (FIG. 10B), and, then halved inlength by bending as shown in FIG. 10C at the center of the accordionfolded configuration for a twice-kind folded configuration for shippingand storage in a reduced shipping size or state as shown in FIG. 10D.

FIG. 11E shows a filter assembly according to at least one embodimenthaving a filter media element termed herein as a “magnetic foldablefilter.” The frame (FIG. 11D) includes four linear L-channel segmentsjoined by four corner clips. The filter media element (FIGS. 11A-11C)includes multiple panels joined together by creases or fold linesparallel to the edges of the rectangular filter media element. Thus thefilter media element can be folded along crease lines extending in twodimensions so as to be map folded or otherwise reduced to a minimizedconfiguration (see “ship size” of FIG. 11A) convenient for shipping andstorage. Magnetic strips along the outer edges of the filter mediaelement engage the frame, which also has magnets or other appropriatematerial for magnetic attachment. The frame may have one (FIG. 11D) ormore grate arms spanning between opposing outer frame segments so as toform a grate to support the filter media element.

FIG. 12A shows a filter assembly according to at least one embodimenttermed herein as a “flat filter sandwich design.” A flexible andfoldable filter media element is captured between interlocking teeth oftwo rectangular frame sections. As shown in FIG. 12C, extra edgeportions of the filter media element, serving as a flexible outergasket, extend outward from the sides of the frame formed when the twoframe sections are engaged by their interlocking teeth (FIG. 12B).

FIGS. 13A-13C show a variable frame and grate assembly according to atleast one embodiment termed herein as a “foldable frame snap in grid.”The assembly includes a peripheral frame of linear segments arranged ina rectangular form in the filter plane. The linear segments are formedby folding an L-channel strip, which is foldable at spaced notchesformed in the filter plane face of the strip. The notches are wedgeshaped, having a wide mouth and narrowing inward toward a hole thatretains knobbed posts of a snap-in mesh or grid that forms a grate wheninstalled. The notches and posts are equivalently spaced so as to alignand permit variable sizing. Any excess of the frame strip can be cutfree of the rectangular form, and the mesh or grid is cut or preformedto the desired dimensions. The engagement of the posts along the outeredges of the mesh with the holes in the frame segments maintains theassembly in any final desired dimensions and configuration. Variousfilter media elements can be installed or used with the assembly ofFIGS. 13A-13C, with support across the filter plane by the grate.

FIG. 14 shows a cover for a filter assembly, the cover having a logo orother graphic for aesthetic purpose according to at least oneembodiment. The cover may, for example, have cutout areas so as to serveas a grate to support a filter media element. In the illustratedembodiment, an elephant logo or graphic is represented. Other graphicillustrations, logos, and artworks are within the scope of thesedescriptions.

FIGS. 15A-15C show an expandable filter media element, according to atleast one embodiment, in three configurations. The filter media elementhas a pair of panels that can each be folded along parallel accordionfold lines to collapse the filter media element in one of two filterplane dimensions. The two panels are joined by an edge strip having acentral crease or fold line facilitating the bending of the edge stripso as to halve the filter media element in length thus further reducingthe filter media element in the second of the two filter planedimensions. Thus, the expandable filter media element can be reduced toa collapsed and folded configuration for shipping and storage.

FIGS. 16A-16B show a frame assembly according to at least one embodimenttermed herein as a “linear frame−straight+corners.” The assemblyincludes four linear L-channel segments defining an outer rectangularform of variable dimensions in the filter plane according to the lengthsof the segments. The four corner junctions of the segments aremaintained by a corner clip at each corner. Two diagonal inner framesegments, serving as a grate to support a filter media element, crossand intersect at the center of the frame. Each inner frame segment spansthe interior area of the frame between diagonally opposing corners. Theinner frame segments snap into place, with a joint at their centers atwhich they are engaged. The frame segments are partially rotatablerelative to each other at the joint permitting the joined inner framesegments to be placed in an almost parallel reduced configuration forshipping and storage. The variable frame assembly is useful to supportor strengthen various filter assembly embodiments described herein.

FIG. 17 shows a variable frame and grate or filter assembly according toat least one embodiment termed herein as a “planar frame.” The assemblyincludes a filter plane element supported by a peripheral frame oflinear segments arranged in a rectangular form. The illustrated filterplane element can represent a grate, a filter assembly, and both amongother examples. The frame segments are angle cut, for example at 45degrees, at their ends to define abutting corner joints.

FIGS. 18A-18C show a filter assembly according to at least oneembodiment. A filter media element (FIG. 18B) having a rectangularperiphery is supported by a removable grate having four arms extendingoutwards from a central hub, on which a logo or other graphic is shownin FIG. 18C.

FIGS. 19-20C show a filter assembly, according to at least oneembodiment, which can be twice folded from an expanded rectangularconfiguration to a reduced configuration convenient for shipping andstorage. The filter assembly includes a filter media element supportedby a rectangular peripheral frame of foldable linear segments and agrate defined by a grid of arms crossing the rectangular interiordefined within the peripheral frame.

The filter media element of FIGS. 19-20D, and various other filterassemblies and media elements illustrated in the drawings and describedherein, may have a layered filter medium using an undulating non-wovenpile layer and a supporting grid fiber layer.

FIGS. 21A-21C show a foldable filter media element 2110, according to atleast one embodiment, in an expanded state. A pattern of crease or foldlines facilitate folding of the media element from the expandedconfiguration (FIG. 21A) to a reduced configuration (FIG. 2C) convenientfor shipping and storage. The reduced configuration has an area that isone fourth in size relative to the expanded configuration in the filterplane. The particularly illustrated fold pattern is termed herein an“origami crane fold.” Avantageously, the four outer corners 2112 of theexpanded configuration are brought together in the reduced configurationat a location diagonally across the reduced configuration from thecenter 2114 of the media element, which occupies an opposite corner ofthe reduced configuration.

FIG. 22A is a shipping or storage package into which a filter mediaelement, according to at least one embodiment, can be placed in areduced configuration as shown in FIG. 22B. The filter media element forexample may be that of FIGS. 21A-21C or others according to variousembodiments. The package shown in FIGS. 22A-22B is a soft-walledenvelope or bag having a sealing flap shown as open.

In the filter assembly according to FIG. 23, a peripheral frame segment2300 serves as a clip retaining a screen 2320 and an expandablereplaceable filter element 2310. The frame segment may, for example, bean extruded strip segment. In cross-sectional view, the frame segmenthas an outer edge wall 2302 and three inward extending strips betweenwhich two slots are formed for respectively retaining the screen andfilter. The screen is retained in a first slot defined between a lowerstrip 2304 and a central strip 2306. The filter element is retained in asecond slot defined between the central strip and an upper strip 2308. Adownward extending bead 2309 along the lower face of the inward edge ofthe upper strip helps to retain the filter element. The filter element2310 has an accordion folding filter medium 2314 and an edge cuff 2312in which a peripheral edge of the filter medium is captured. The filterelement is retained along the frame segment by engagement of the edgecuff 2312 within the second slot and with the bead 2309.

In the filter assembly according to FIG. 24, a peripheral frame segmentserves as a clip retaining a screen and an expandable replaceable filterelement. The frame segment may, for example, be formed of extruded stripsegments. In cross-sectional view the frame segment has an outer edgewall and three inward extending strips between which two slots areformed for respectively retaining a screen and a filter element. Thescreen is retained in a first slot defined between a fixed lower stripand a fixed central strip. The filter element is retained in a secondslot defined between the central strip and a folding upper strip. Theupper strip is connected to the edge wall by a hinge allowing the secondslot to open to receive the filter element and close upon the filterelement for retention. The filter element has an accordion foldingfilter medium and an edge cuff in which a peripheral edge of the filtermedium is captured. The filter element is retained along the framesegment by engagement of the edge cuff within the second slot and withthe folding upper strip.

In the filter assembly according to FIG. 25, a peripheral frame segmentserves as a clip retaining an expandable replaceable filter elementbetween front and back screens. The frame segment may, for example, bean extruded strip segment. In cross-sectional view the frame segment hasan outer edge wall and three inward extending strips between which twoslots are formed for retaining the screens and filter element. The backscreen is retained in a first slot defined between a lower strip and acentral strip. The filter element and front screen are retained in asecond slot defined between the central strip and an upper strip. Aninward barb-like fold along the edge of the front screen helps to retainthe filter element. The filter element has an accordion folding filtermedium and an edge cuff in which a peripheral edge of the filter mediumis captured. The filter element is retained along the frame segment byengagement of the edge cuff within the second slot and with thebarb-like fold of the upper screen.

In the filter assembly according to FIG. 26, a peripheral frame segmentserves as a clip retaining an expandable replaceable filter elementbetween front and back screens. The frame segment may, for example, bean extruded strip segment. In cross-sectional view the frame segment hasan outer edge wall and four inward extending strips between which threeslots are defined. A back slot, a central slot, and a front slot aredefined for respectively retaining the back screen, filter element, andfront screen. The filter element has an accordion folding filter mediumand an edge cuff in which a peripheral edge of the filter medium iscaptured. The filter element is retained along the frame segment byengagement of the edge cuff within the central slot.

In the filter assembly according to FIG. 27, a peripheral frame segmentserves as a clip retaining a screen and an expandable replaceable filterelement. The frame segment may, for example, be an extruded stripsegment. In cross-sectional view the frame segment has an outer edgewall and three inward extending strips between which two slots areformed for respectively retaining the screen and filter element. Thescreen is retained in a first slot defined between a lower strip and acentral strip. The filter element is retained in a second slot definedbetween the central strip and an upper L-shaped strip. A bezel clipmounts onto an upper extending arm of the L-shaped strip and furtherengages to retain the filter element. The filter element has anaccordion folding filter medium and an edge cuff in which a peripheraledge of the filter medium is captured. The filter element is retainedalong the frame segment and bezel clip by engagement of the edge cuffwithin the second slot and with the bezel clip.

In the filter assembly according to FIG. 28, a peripheral frame segmentserves as a clip retaining a screen and an expandable replaceable filterelement. The frame segment may, for example, be an extruded stripsegment. In cross-sectional view the frame segment has an outer edgewall and three inward extending strips between which two slots areformed for respectively retaining the screen and filter element. Thescreen is retained in a first slot defined between a lower strip and acentral strip. The filter element is retained in a second slot definedbetween the central strip and an upper strip. A bezel clip mounts ontothe upper strip and further engages to retain the filter element. Aninward extending bead along a lower face of the bezel clip helps toretain the filter element. The filter element has an accordion foldingfilter medium and an edge cuff in which a peripheral edge of the filtermedium is captured. The filter element is retained along the framesegment and bezel clip by engagement of the edge cuff within the secondslot and with the bead of the bezel clip.

FIG. 29A shows a filter assembly, according to at least one embodiment,in which a peripheral frame retains an expandable replaceable filterelement. The frame, as shown in FIG. 29B, has four linear segments, eachhaving a hinging bezel that snaps onto a respective edge of the filterelement. The filter element is foldable for reduction to convenient sizefor shipping and storage as shown for multiple embodiments of thedrawings. The frame is shown without the filter element in the other ofthe two views.

FIGS. 30A and 30B show a filter assembly according to at least oneembodiment. A peripheral frame retains an expandable replaceable filterelement. The frame has four linear segments. The filter element isfoldable for reduction to convenient size for shipping and storage asshown for multiple embodiments of the drawings. The frame is shown withthe filter element in place in FIG. 30A, and with the filter elementraised in FIG. 30B. The filter element has a C-channel outer sub-frameand a filter media element having edges retained by the outer sub-frame.A particular embodiment of a support insert is shown as a grid of armsparallel to the sub-frame edges and joined at the center of the filterelement to serve as a grate.

FIGS. 31A and 31B show a filter assembly according to at least oneembodiment. A peripheral frame retains an expandable replaceable filterelement. The frame has four linear segments. The filter element isfoldable for reduction to a convenient size for shipping and storage asshown for multiple embodiments of the drawings. The frame is shown withthe filter element in place in FIG. 31A, and with the filter elementraised in FIG. 31B. The filter element has a C-channel outer sub-frameand a filter media element having edges retained by the outer sub-frame.A particular embodiment of a support insert is shown as a grid of arms,each of two arms extending corner to corner angled relative to thesub-frame edges and joined at the center of the filter element to serveas a grate.

FIGS. 32A and 32B show a filter assembly according to at least oneembodiment. A peripheral frame retains an expandable replaceable filterelement. The frame has four linear segments. The filter element isfoldable for reduction to convenient size for shipping and storage asshown for multiple embodiments of the drawings. The filter element has aC-channel outer sub-frame and a filter media element having edgesretained by the outer sub-frame. A particular embodiment of a supportinsert is shown as a single arm having a tapered end that engagesremovably under an edge of the sub-frame so as to support and retain thefilter media element. The support insert is shown in place in FIG. 32A,and raised in FIG. 32B.

FIG. 33A shows a filter assembly, according to at least one embodiment.A peripheral frame retains an expandable replaceable filter element. Theframe has four linear segments joined at four corners. The frameincludes fasteners at the four corners to retain the filter element. Thefilter element is foldable for reduction to convenient size for shippingand storage as shown for multiple embodiments of the drawings. Thefilter element (FIG. 33B) has a C-channel outer sub-frame and a filtermedia element having edges retained by the outer sub-frame. A particularembodiment of a support insert is shown in FIG. 33C as a grid of fourarms attached to a central hub. The arms can fold together out of thefilter plane for reduction to a convenient size. For use, the armsspread apart into the filter plane, extending at 90 degree intervals, toengage the sub-frame or frame segments so as to serve as a grate asshown in FIG. 33A.

FIGS. 34A-34C show a similar embodiment as shown in FIG. 33A-33C. InFIGS. 34A-34C the four arms of the support insert in this embodimentmeet and are joined by a hub element at the center of the rectangularform of the filter element.

FIG. 35A shows a filter element in a folded state in a package,according to at least one embodiment, for shipping or storage. FIG. 35Bshows the filter element of FIG. 35A, removed from the package and atleast partially unfolded. FIG. 35C shows the foldable filter elementhaving magnetic strips at outer edges to engage corresponding magnets ormagnetically responsive materials at the inner edges of a frame.

FIGS. 36A-36B show a frame and grate for a filter assembly according toat least one embodiment termed herein as a “snap frame.” The assemblyincludes four linear segments defining an outer rectangular form ofvariable dimensions in the filter plane according to the lengths of thesegments. A grid of spaced arms defining rectangular spaces therebetweenextends across the interior of the filer assembly to serve as a grate tosupport a filter media element. At least one clip along each framesegment secures the grid to the frame. The clips may secure the edges ofa filter media element to the frame and grid as well. A variety ofalternative grid patterns are also shown in FIG. 36C.

FIG. 37A shows an edge portion of a filter assembly according to atleast one embodiment. A peripheral frame segment serves as a clipretaining an expandable replaceable filter element and optionally ascreen (see for example FIG. 28 for a screen). The frame segment may,for example, be an extruded strip segment. As shown in FIG. 37B, theframe segment has an outer edge wall and three inward extending stripsbetween which two slots are formed for respectively retaining the screenand filter element. The screen or grate may be retained in a first slotdefined between a lower strip and a central strip. The filter element isretained in a second slot defined between the central strip and an upperstrip. A bezel clip, shown separately in FIG. 37D, mounts onto the upperstrip as shown in FIG. 37B, and further engages and retains the filterelement as shown in FIG. 37A.

FIG. 38C shows a filter assembly according to at least one embodiment. Afilter element (FIG. 38A), which is foldable for reduction to convenientsize for shipping and storage, has an outer sub-frame and a filter mediaelement having edges retained by the outer sub-frame. A grid of lineararms (FIGS. 38B and 38C) attached together at the center of the assemblyin the filter plane serves as a grate to support the filter mediaelement.

FIG. 39A shows a filter assembly, according to at least one embodiment,in which a filter element, which is foldable for reduction to convenientsize for shipping and storage, has an outer sub-frame and a filter mediaelement having edges retained by the outer sub-frame. A grid of lineararms attached together at the center of the assembly in the filter planeserves as a grate to support the filter media element. In the expandedconfiguration, the filter assembly has a square form. The four arms arejoined by a folding bracket hub (FIGS. 39B-39D), termed herein a“boomerang bracket,” having a hinge aligned along a 45 degree centralaxis of the filter media element relative to the sides of the squareform. Folding the bracket hub about the hinge advantageously facilitatesreducing the filter element to the illustrated fold pattern of FIG. 21C.

FIGS. 40A-40C show a filter assembly according to at least oneembodiment. The illustrated filter assembly is similar to that shown inFIG. 39A, and is foldable by use of the folding bracket hub to theillustrated fold pattern of FIG. 21C, also shown in FIG. 40C.

FIGS. 41A-41C further show the construction of the folding bracket hubof FIGS. 39B-39D, according to at least one embodiment. The foldingbracket hub has two base elements, joined by the hinge, which arebrought together when the bracket hub is reduced to the foldedconfiguration, and which spread into the filter plane when the brackethub is opened to the expanded configuration. Each base element carriestwo sockets, each for receiving an inner end of an arm in male-femaleengagement. The sockets are directed at 90 degree intervals from eachother so that, in the expanded configuration with an arm carried by eachsocket, the arms are arranged at 90 increments in the filter plane, eachextending outward to a respective outer edge of the filter assembly (seeFIGS. 39A and 40A for example).

FIG. 42 shows a variety of arms for use with the folding bracket hub ofFIGS. 41A-41C. The sockets of the bracket hub in FIG. 41A are shown ascircularly cylindrical with longitudinal slits to accommodate some sizerange or shape variety in the arms they retain. The sockets in otherembodiments may take other forms corresponding to or otherwiseaccommodating any of the arms shown in FIG. 42. Other cross-sectionalshapes of both arms and sockets are within the scope of thesedescriptions beyond those explicitly illustrated.

FIGS. 43A and 43B show an edge treatment for a filter media element,according to at least one embodiment. An edge treatment, in oneembodiment, includes a C-channel strip that clips onto and retains anedge of the filter media element. The C-channel strip for example may berigid along its length, and may be formed for example by extrusion. Anedge treatment, in another embodiment, includes a deformable C-channelgasket, formed of foam or other resilient compressible material, servingas a seal between edges of the filter media element and any outer frameor other host structure.

FIG. 44 shows an expandable filter media element having an advantageousfold pattern to facilitate reduction of the media element two dimensionsso as to take up a smaller area for convenient shipping, storage, orvariable sizing.

FIG. 45A shows an expandable filter media element having a preferentialfold pattern to facilitate two-dimensional reduction of the mediaelement for convenient shipping, storage, or variable sizing. In FIG.45A, a collapsible cross grate having four arms connected to a centralstrip can be formed of profiled spring steel having a cylindricalconcave side and opposing cylindrically convex side. Such material withsuch form is advantageously flexible and biases toward an expandedconfiguration when deployed.

FIG. 46A shows an expandable filter media element 4600 having a filtermedium 4602 that features an advantageous fold pattern to facilitatetwo-dimensional reduction of the filter media element 4600 forconvenient shipping, storage, or variable sizing. A collapsible crossgrate 4604 having four arms 4606 connected to a central strip 4610 canbe formed of profiled spring steel elements having opposing curvatureson opposing sides. Additional edge segments 4608 of same, similar, orother semi-rigid resilient material are shown along edges and corners ofthe media element 4600. As shown in FIG. 46B, the profiled spring steelelement 4612 has a cylindrical concave (channeled) side 4614 and anopposing cylindrically convex side 4616. Advantageously, the profiledspring steel 4612 is self-biased from any flexed or folded state towardits linear state, in which it extends along its longitudinal channelaxis 4620 defined along its cylindrically concave side 4614, and thusprovides opening and unfolding forces and self-expanding action in thefilter media element 4600 to the planar state of FIG. 46A when a foldedfilter media element is released for example from a package or otherbinding used for shipping and storage in a reduced state.

FIG. 47A shows a first side of an expandable filter element having acreased filter media element having a preferential fold pattern tofacilitate two-dimensional reduction of the media element for convenientshipping, storage, or variable sizing. The filter element is engagedalong its outer edges by a foldable frame having mechanical hinges forsize reduction for storage and shipping, and expansion for deployment.The filter element may have a pleated paper top layer (FIG. 47B) over afoam substrate (FIG. 47C), according to at least one embodiment.

FIG. 48A shows a second side of the expandable filter element of FIG.47A. The filter media element has four quadrants, with each beingsymmetric with a diagonally opposing element, such that two quadranttypes each having a characteristic fold pattern are shown. Twofirst-type fold quadrants 4802 are diagonally opposed across the centerof the media element, and two second-type fold quadrants 4804 arediagonally opposed across the center of the media element adjacent toand between the first-type fold quadrant 4802. As shown, a foldingbracket hub and arms may be included with the expandable filter elementof FIG. 48A. Semi-rigid struts, for example constructed of a plasticsuch as PET, may also be included along edges of the filter element. Anedge treatment, formed of foam or other resilient compressible material(FIG. 48B), may also be included serving as a seal between edges of thefilter element and any outer frame or other host structure.

FIG. 49 shows a first side (“TOP VIEW”) of an expandable filter having acreased filter media element having an advantageous fold pattern tofacilitate two-dimensional reduction of the media element for convenientshipping, storage, or variable sizing. The filter element is engagedalong its outer edges by a foldable foam frame, which may serve as aseal between edges of the filter element and any outer frame or otherhost structure.

FIG. 50 shows a second side (“BACK VIEW”) of the expandable filterelement of FIG. 47A. A grid of linear arms attached together at thecenter of the assembly in the filter plane serves as a grate to supportthe filter media element. In the expanded configuration, the filterassembly has a square form. The four arms are joined by a folding hubhaving a locking hinge with springs. The hub is foldable along two axes,perpendicular to each other and each parallel to a side of the squareform of the expanded filter assembly. Four arms extend from the hubdefining four square quadrants in the square form. The folding hub andarms define a folding grate for supporting the filter media element.FIGS. 51 and 52 show the folding grate of FIG. 50 without a filter mediaelement.

FIG. 53 shows an expandable filter element similar to that of FIG. 50.The folding hub of FIG. 53, in contrast with that of FIG. 50, has anopen central square area, which may advantageously accommodate gatheredfilter media at the center of the fold pattern when the filter elementis reduced by folding. FIG. 54 is an enlarged view of a central portionof the filter element of FIG. 53, showing the open central area andspring elements of the folding hub. FIG. 55 shows the folding grate ofFIG. 50 without a filter media element.

Particular embodiments and features have been described with referenceto the drawings. It is to be understood that these descriptions are notlimited to any single embodiment or any particular set of features, andthat similar embodiments and features may arise or modifications andadditions may be made without departing from the scope of thesedescriptions and the spirit of the appended claims.

What is claimed is:
 1. An air filter assembly for a heating andventilation air conditioner (HVAC) system, the filter assemblycomprising: a filter media element having peripheral edges; and a frameincluding flexible arms each engaging and supporting a respective one ofthe peripheral edges of the filter media element, each flexible armbeing self-biased toward a linear state such that the air filterassembly is biased by the flexible arms to a rectangular configurationin which the filter media element is in an expanded state for use withinan airflow of an HVAC system.
 2. The air filter assembly of claim 1,wherein the linear flexible arms bias the frame toward a rectangularconfiguration of variable dimensions.
 3. The air filter assembly ofclaim 1, wherein the frame comprises four flexible arms and fourcorners, each corner defined by intersecting ends of two adjacentflexible arms.
 4. The air filter assembly of claim 1, wherein the airfilter assembly is collapsible, by flexure of the flexible arms, fromthe rectangular configuration to a reduced configuration for shipping orstorage.
 5. The air filter assembly of claim 4, wherein the filterelement is at least twice folded in the reduced configuration of the airfilter assembly.
 6. The air filter assembly of claim 1, furthercomprising an edge treatment forming a seal between the filter mediaelement and frame.
 7. The air filter assembly of claim 1, wherein eachflexible arm comprises a spring steel element.
 8. The air filterassembly of claim 7, wherein the flexible arms together provide openingforces to the filter media element toward the expanded state when theair filter assembly is released from a reduced configuration in apackage used for shipping.
 9. The air filter assembly of claim 7,wherein each flexible arm has a cylindrical concave side and an opposingcylindrically convex side.
 10. The air filter assembly of claim 9,wherein each flexible arm is self-biased from a flexed or folded statetoward the linear state thereof, in which the flexible arm extends alonga longitudinal channel axis defined along the cylindrically concave sidethereof.
 11. The air filter assembly of claim 1, wherein the filtermedia element comprises an undulating non-woven pile layer.
 12. The airfilter assembly of claim 11, wherein the filter media element comprisesa grid fiber layer.
 13. The air filter assembly of claim 1, furthercomprising edge treatments attached to respective peripheral edges ofthe filter media element.
 14. The air filter assembly of claim 1,further comprising an edge treatment for forming a peripheral seal. 15.The air filter assembly of claim 14, wherein the edge treatmentcomprises at least one of a deformable gasket, a flange, and a layer forforming a seal at a peripheral edge of the filter media element.